Father is bipolar and has manic episodes where he goes missing. 100% FREE

Father is bipolar and has manic episodes where he goes missing. want an app to track his iphone without him knowing when he`s manic? Friend`s father has known bipolar episodes, has disappeared for weeks, cops called, etc. He is paranoid when like this, and just need an app that will let us find his phone when he`s having a manic episode and make sure he`s safe. This means it needs to be in the background and difficult to find and turn off.